I hope that this is ok for me to post as a BS.
As a male, I can firmly say that to me, the PA is much, much worse. Haunting, is the word I will use. The EA I can conceptualize, to a degree. That's not to say that I'm giving it the 'ok'. Using the slippery slope metaphor, I think most people have stood at the top of that slope and felt the *tug* of being pulled downhill. I can understand how, with bad boundaries and the right (wrong?) set of relationship circumstances, you can go from platonic friend, to oversharing personal info, to admitting romantic feelings (while not acting on them), etc., and so on. 'NJF' pretty much spells out exactly how it happens.
I've met attractive people who I found interesting while I've been married, but while I've had problems with being flirty (not excusing, just being honest), I've always been very, very careful about not complaining/talking about my married life in any negative light with the opposite sex. I always felt it sent the 'wrong message'...as though complimenting someone on their looks doesn't. Logic fail. That doesn't mean that the temptation to do so wasn't there, only that for some reason within myself, it felt more wrong inside my head to discuss my marital issues or problems with my wife than it did to tell a young lady she was pretty or something else flirty, and that was the boundary I chose not to cross. However, my WW was devastated when she found me being flirty on FB, especially since she always felt I didn't compliment her enough as it was. Devastated. And as a WH (at that point) I didn't have SI and handled the situation mostly like an idiot. I did NC, and have maintained for 3 years, but as far as being understanding about how long it took her to heal, I screwed it up.
When I caught my wife having a EA back in May, I was really upset, but not totally shocked. I was never around due to school, work, and an internship. Again, I could understand how it happened, to a degree. However, when it went underground in August and became a PA, it's been much, MUCH harder for me to shake. It's not just the mind movies associated with the PA, it's HOW DAMN HARD she had to work to make it happen. I never really considered for a second having a full-blown EA/PA, for a lot of reasons.
I'm kind of lazy, and they seem like a lot work.
I have a hard enough time figuring out/dealing with my wife's emotions as they relate to me, and to deal with two people's feelings, hopes, dreams, etc., seems exhausting, frankly. In fact, when I discovered my WW's PA, one of the first things she said to me after we established NC was how relieved she was that she no longer had to deal with juggling two people's feelings. I didn't empathize.
Don't get me wrong, the thought of how it would affect and destroy my wife and family would be the foremost reason, I was just listing others as well.
Again, as a guy, I think it's the PA that haunts me the most. Maybe it's related to some neanderthal portion of my brain that views my WW as 'submitting' or 'giving in' to another man, and as him 'besting' me in some sort of evolutionary competition. He 'took what was mine' and so, in the recesses of my mind 'he must be more evolutionarily fit (better)' than me.